Apple released a big new update for iPhones and iPads on Monday, with nifty features like Find My AirPods and Siri improvements, but most people won't even notice the biggest change.

As part of the iOS 10.3 update, Apple changed a basic part of how every iPhone and iPad works — its file system, or, basically the way the computer stores data and knows where and how to find it.

With Monday's update, Apple updated iPhones and iPads to its new "Apple File System," upgrading from "HFS+," which was first developed over 30 years ago.

It was a smart move for the future. Apple File System "is optimized for Flash/SSD storage and features strong encryption ... and improved file system fundamentals" and should help iPhones and iPads run faster and more smoothly going forward.

But this was a risky move, too. Because a computer's file system is a fundamental part of the device, there was a chance if something went wrong, it could've deleted some people's files, as Business Insider previously reported.

The good news is that 12 hours after the update went out — and was downloaded by millions — there don't seem to be any major problems with the transition to AFS. That's a big achievement for the Apple employees working on it.

If something had gone wrong, Apple would've heard about it, and it could've been bad if people actually lost their files. The one complaint is that the update takes a long time to install, and that's most likely due to rewriting the entire file system.

Apple could've made a big deal about this achievement. I'm sure people at Microsoft and Google, which have to push similar major updates, took notice. But instead, it pulled it off without much fanfare, and most people won't even know their iPhones have changed in a big way.